Elucidating Serotonergic Mechanisms Regulating Cardiovascular Recovery After Grafting Embryonic Raphe Neurons into the Injured Rat Spinal Cord

项目总结/摘要 第6胸段（T6）或以上的脊髓损伤（SCI）通常会导致脊髓上神经功能丧失。 调节心血管功能。这种功能障碍表现为异常的静息血流动力学和 发生直立性低血压和自主神经反射异常（AD）。总的来说，这些违规行为 心血管功能障碍是人群发病和死亡的主要原因之一。 虽然目前有药理学和预防措施来缓解这些问题，但它们 缺乏长期疗效，并且不能解决潜在的脊髓上连接丧失。最近我们 发现脊髓损伤后移植中缝核源性神经祖细胞/干细胞（RN-NPCs）部分恢复 血流动力学调节更具体地说，我们发现移植物恢复了中缝核之间的连接 细胞群和交感神经节前神经元。此外，沉默肾上腺素能 受体5 HT 2A导致功能恢复的丧失。因此，我们假设功能恢复 移植后的中枢神经系统通过脊髓上和脊髓内的神经元能机制介导。目标1： 将RN-NPCs移植到T4挤压损伤的大鼠中，并测量心血管输出量，包括静息 血流动力学以及AD频率和严重程度。随后，我们将再次损伤移植部位上方的大鼠 重新评估所有血液动力学参数这将决定功能恢复是否取决于 与移植物的脊髓上连接。在目标2中，我们将采用化学遗传学技术来沉默多巴胺能受体， RN-NPC移植后宿主中缝尾核神经元的变化，以确定是否存在脊髓上的多巴胺能调节 心血管功能已经恢复。在目标3中，我们将使用相同的化学遗传学工具来沉默 移植物衍生的肾上腺素能神经元，阐明这些神经元是否促进血流动力学恢复。我们还将 给予肾上腺素能和去甲肾上腺素能受体拮抗剂，以检查哪些脊髓受体参与 重建心血管调节总的来说，这些结果将为潜在的临床研究提供指导。 翻译以减轻SCI后的血流动力学功能障碍。

PROJECT SUMMARY/ABSTRACT Spinal cord injury (SCI) at the 6th thoracic level (T6) or above often results in the loss of supraspinal regulation over cardiovascular function. This dysfunction manifests as abnormal resting hemodynamics and the development of orthostatic hypotension and autonomic dysreflexia (AD). Collectively, these irregularities mark cardiovascular dysfunction as one of the leading causes of morbidity and mortality among the population. Although there are current pharmacological and preventative measures in place to mitigate these issues, they lack long-term efficacy and do not address the underlying loss of supraspinal connectivity. Recently, we discovered grafting raphe nuclei-derived neural progenitors/stem cells (RN-NPCs) after SCI partially restores hemodynamic regulation. More specifically, we found that the graft restores connectivity between raphe nuclei cell populations and sympathetic preganglionic neurons in the spinal cord. Moreover, silencing serotonergic receptor 5HT2A resulted in the loss of functional recovery. Therefore, we hypothesize that functional recovery after grafting is centrally mediated through supraspinal and intraspinal serotonergic mechanisms. In Aim 1, we will graft RN-NPCs into rats sustaining a T4 crush injury and measure cardiovascular output including resting hemodynamics, and AD frequency and severity. Subsequently, we will reinjury the rats above the transplant site and reevaluate all hemodynamic parameters. This will determine if functional restoration is contingent on supraspinal connectivity with the graft. In Aim 2, we will employ chemogenetic techniques to silence serotonergic neurons of the host caudal raphe nuclei after RN-NPC grafting to identify if supraspinal serotonergic regulation of cardiovascular function has been reestablished. In Aim 3, we will use the same chemogenetic tools to silence graft-derived serotonergic neurons, elucidating if these neurons facilitate hemodynamic restoration. We will also administer serotonergic and noradrenergic receptor antagonists to examine which spinal receptors are involved in reestablishing cardiovascular regulation. Collectively, these results will provide guidance for potential clinical translation to mitigate hemodynamic dysfunction after SCI.